Various solutions for adjusting a variable pitch propeller of turbo-engines are known. In a book by Petermann, "Turbo-Engines" on page 19, FIG. 1.2.2.2, an adjustment gear transmission of a propeller pump is shown, which has a hollow drive shaft within which an axially longitudinally movable adjustment spindle transmits a force to the blades in a propeller head. The end of the drive shaft that is remote from the pump has slip-ring contacts, through which electrical power can be conducted to an electric motor integrated therein. The electric motor transfers its rotational speed and its torque to a step-down transmission connected to a spindle nut. The spindle nut is mounted axially and radially in the end of the pump shaft and transmits the rotary motion to an adjustment spindle. This proposed design requires a large amount of area and construction expense and has the disadvantage that the slip tings constitute a trouble spot for the transmission of electrical current.
JP59-176 498 discloses another proposed solution. The shaft is here constructed in parts, such that an electrical adjustment mechanism is integrated into a drive part of the shaft. A bearing for the rotor of the electric actuating drive is disposed at that end of the first shaft part which is remote from the propeller. The rotor bearing is disposed next to a coupling flange in such a way that it can move axially. By means of an adjoining external thread, the rotary motion of the motor can be converted into an axial motion. The axial motion of the rotor acts on a yoke situated inside the coupling of the two-part shaft, and transmits axial forces to a push rod disposed inside the first shaft part. Due to the overdimensioned long stator part and due to the thread which interacts with the rotor, the rotor moves axially inside the stator and creates the adjustment forces. However, this proposed solution is a very expensive design and exhibits high electric losses. The smallest external influences, such as dirt and the like, can jeopardize the function of this adjustment mechanism, because the sealing gap diameters are sometimes disposed on large diameters.